In the post-WW2 years, most of his work was dedicated to various
efforts to prevent further wars, especially wars with nuclear
weapons. This is the subject of much of the last third of his
autobiography; for me, this was perhaps the least interesting part
of his autobiography. I guess I'll never be able to truly appreciate
how it must have felt in the cold war years when many people
genuinely worried about the possibility that a nuclear world war
might erupt and bring about the extinction of the vast majority of people
in the world.
One of the earliest memories from my childhood is hearing news on the radio
about one of the Reagan-Gorbachev negotiations to curtail the nuclear
arms race. By then, the mid-80s, the threat of nuclear war seemed so remote
as to be of no consequence. MAD
may sound insane, but I really think it worked jolly well. And yet it seems
clear that for many people in the 50s, 60, perhaps 70s, nuclear war was
an entirely realistic concern.

Russell felt that, now that the major powers are in possession of
nuclear weapons, any large-scale war between them would be disastrous
for the whole world; therefore, wars must be prevented altogether.
As long as nuclear weapons exist, there is also the possibility of
a nuclear war being started by accident or mistake; therefore, we
should try to decrease the amount of nuclear weapons in existence
as much as possible. In the long term, there should be a world government
with, of course, sufficient power on its side as to be able to act like a
world policeman and force individual countries to abandon wars.

Of course he was aware that there are many obstacles to this idea of a world government.
For example, people are still often taught to be ‘patriots’:
“At present, children are taught to love their country to the
exclusion of other countries, and among their countrymen in history
those whom they are specially taught to admire are usually those who
have shown most skill in killing foreigners.” (P. 680.)

Regarding a world government, there is a very interesting remark on p. 681:
“Every technical advance in armaments has involved an increase in the
size of States. [. . .] weapons of mass destruction have made
even the greatest States liable to complete destruction.” But I doubt
if this fact alone will be sufficient to encourage the individual states
to accept a world-government above them. In the past, the reason why
advances in military technology led to increases in the size of states
was because there were many states that competed against each other,
and those that weren't large enough to keep up with the technical development
of armaments would eventually lose in this struggle and would be swallowed
by other states. But now a superpower can in principle always defend itself
from attack by other superpowers, at least by destroying the whole world with
nuclear weapons. Therefore there is nothing to really encourage the next
step in the growth of states, namely to a world-state. Either one state would
have to become so much stronger and more advanced than others as to be able
to conquer and occupy them despite the fact that they have nuclear weapons
(which, of course, just might happen, given that the U.S.
spends more money
on its army than the next twenty countries put together);
or there would have to be some external enemy (e.g. Martians :-)),
which would enable the states to step together and form some kind of federation.

He also wrote some fiction in this period. “The writing of these
stories was a great release of my hitherto unexpressed feelings and of thoughts which could
not be stated without mention of fears that had no rational basis.” (P. 525.)

He visited Greece in 1952. “At Tiryns, the guardian of the ancient
citadel bemoaned the fact that it had been very badly restored. Upon being asked
when this distressing renovation had taken place, he replied, ‘During the
Mycenaean times’.” (P. 560.)

“I realised then that the Christian outlook had a firmer hold upon me than I had imagined. The hold was
not upon my beliefs, but upon my feelings. It seemed to me that where the Greeks differed from the modern world
it was chiefly through the absence of a sense of sin, and I realised with some astonishment that I, myself,
am powerfully affected by this sense in my feelings though not in my beliefs.” (P. 561.)

His various anti-nuclear efforts in the post-war decades included,
for example, preparing various broadcasts on this subject for the BBC (p. 564);
he prepared a manifesto against nuclear weapons and got a number of eminent
scientists, from both East and West, to sign it (pp. 566–71;
Einstein was among the signatories as well; he signed it mere days before
his death, p. 567); attended numerous conferences and meetings;
wrote an open letter to Eisenhower and Khrushchev (addressing them as “Most
Potent Sirs”, p. 596); participated in the Campaign for
Nuclear Disarmament (which advocated unilateral nuclear disarmament of Britain;
p. 596); as well as in the Direct Action Committee (which tried to
bring these issues to the notice of the public through nonviolent
protests and civil disobedience; p. 597; e.g. a large sit-down in Trafalgar Square
on February 18, 1961; p. 607), and later the Committee of 100
(pp. 605, 632); he wrote a book titled
Common Sense and Nuclear Warfare (pp. 598–9);
he wrote a letter to U Thant
with suggestions on organizing a ‘Balancing Committee’
to mediate East-West problems (p. 647); letters to
Nehru
and Chou En-Lai,
encouraging a peaceful settlement of the
Sino-Indian border dispute
(pp. 648–51); etc. He also made efforts to help people who are
unjustly imprisoned (p. 653). Finally the work and expenses grew
beyond what he could personally handle, so he established two non-profit
foundations to carry on the work (the Bertrand Russell Peace Foundation
and the Atlantic Peace Foundation; pp. 656–8).

Here's a curious observation he wrote in 1950, living in the same house
as his son John and John's wife Susan: “I suffer also from entering
into the lives of John and Susan. They were born after 1914, and are therefore
incapable of happiness.” (P. 582.) Of course, if taken
literally, such a statement is ridiculous. But what he means, I guess,
is that he feels the first world war brought a major and fundamental change
in the outlook of the people; that there was a really important difference
between the optimistic belief in progress that characterized much of the
18th and 19th centuries, all the way up to the WW1, and the post-WW1 period,
where any such optimism was impossible after the war(s) showed all too clearly
how great is the risk that human civilization will eventually destroy itself.
We often imagine that there must have been such a change in outlook;
but it's a rare instance that I see someone describe it so explicitly
as to say that people born after 1914 are incapable of happiness.
Of course, we must admit that this is far from the first instance in
history when many people felt that everything is going irremediably down
the drain. After all, we know the famous sentence of
Talleyrand:
“He who has not lived in the years before the revolution [of 1789] cannot know what the sweetness of living is.”
And undoubtedly the Romans were saying the same things after being
overrun by the barbarians in the fifth century.

Here's a comment in a similar vein, on the pre-WW1 period:
“When I was young, Victorian optimism was taken for granted. It was thought
that freedom and prosperity would spread gradually throughout the worl dby an orderly process, and it was
hoped that cruelty, tyranny, and injustice would countinually diminish.
Hardly anyone was haunted by the fear of great wars.” (P. 726.)

He briefly mentions that he had supported eugenics
at some point but doesn't give any details (p. 595). Given how notorious eugenics became later,
it would be interesting to know more about this.

An interesting observation from his article Pros and Cons of Reaching Ninety,
published in The Observer (May 13, 1962): “It is a curious
sensation to read the journalistic clichés which come to be fastened
on past periods that one remembers, such as the ‘naughty nineties’
and the ‘riotous twenties’. Those decades did not seem,
at the time, at all ‘naughty’ or ‘riotous’. The habit of
affixing easy labels is convenient to those who wish to seem clever without having to think, but it has very
little relation to reality.” (P. 628.) I guess that with these
stereotypes, there's usually a small grain of truth at the core, but it's then
blown out of all proportion by journalists, memoirists, and other similar people.
This reminds me of the well-known Italian proverb: “even if it isn't true,
at least it's a story well told”. In these circumstances, truth usually
succumbs easily and without putting up much of a fight.

Another interesting passage from the same article: he comments that
many people become mellow and acquiescing as they grow older.
But not he: “Serenity, in the present world, can only be achieved through blindness or brutality.
[. . .] I become gradually more and more of a rebel. [. . .]
Until 1914, I fitted more or less comfortably into the world as I found it.
[. . .] Without having the temperament of a rebel, the course of events
has made me gradually less and less able to acquiesce patiently in what is happening.”
(P. 629.) This is the sort of thing that I find really admirable about Russell.
Most people are perhaps rebellious in youth but become conventional or even conservative
in old age. He, however, was willing to insist on what he felt was right,
and to argue incessantly in its favour, no matter what the conventions
or prevalent opinions thought of it at the time.

A splendid passage from a 1961 anti-nuclear speech, which, as he says, the media
have delighted in taking out of context ever since (pp. 640–1):
“We used to think that Hitler was wicked when he wanted to kill
all the Jews, but Kennedy and
Macmillan and others both in the East
and in the West pursue policies which will probably lead to killing
not only all the Jews but all the rest of us too. [. . .]
I will not pretend to obey a government which is organising the massacre of
the whole of mankind. [. . .] We cannot obey these murderers.
They are wicked and abominable. They are the wickedest people that ever
lived in the history of man and it is our duty to do what we can.”
(However, this passage is now somewhat marred by the unfortunate
fact that ‘wicked’
is more and more often used with a positive connotation, at least in some parts
of the English-speaking world.)

One Lord Gladwyn wrote to Russell, commenting on his plans to set up a foundation:
“I should hope that you would one day be prepared to
advance your proposals in the House of Lords where they could be
subjected to intelligent scrutiny.” (P. 694.)
Russell comments (p. 659): “I refrained, in my reply,
from remarking that on the occasions when I had advanced proposals
in the House of Lords, I had never perceived that my audience, with a few exceptions,
showed any peculiar degree of intelligence”.

On the war in Indo-China: “The pretexts for the ‘escalation’, particularly
the attack upon North Vietnam, reminded me of nothing less than those offered a quarter
of a century earlier for Hitler's adventures in Europe.” (P. 667.)
In response to the atrocities being perpetrated in Vietnam, he
“wrote to a number of people around the world, inviting them to join an
International War Crimes Tribunal” (ibid.). The idea was to investigate
the atrocities and conduct hearings. Although the tribunal of course had
no formal authority, its composition (see the list of members at its
Wikipedia page)
and methods of work certainly gave it great moral weight. Incidentally,
the tribunal also included the Yugoslav historian Vladimir
Dedijer; a couple of years ago I've read his exhaustive (and exhausting)
book The Road to Sarajevo on the background of the assassination
of Archduke Franz Ferdinand.